

VERTEBRATED ANIMALS. 73 



while the fishes, properly so called, partake the tempera- 

 ture of water in which they live, even to the point of freez- 

 ing ; air-breathing animals have the power of resisting 

 both heat and cold, and of preserving nearly the same 

 temperature, whatever that may be in which they are 

 placed. + 



203. It is perhaps true, that to a certain degree, all 

 animals, and even trees, resist both heat and cold so 

 long as the vital principle remains active. But in the 

 lower orders of animals, this power is exceedingly feeble 

 when compared with that which endows quadrupeds 

 and man. 



204. Thus eels become as cold to the touch as the ice 

 in which they may be preserved, and yet the vital princi- 

 ple remains, since these creatures may be thus kept in a 

 torpid state, probably for any length of time, and then 

 again revived to life and activity. It is well known, also, 

 that the gold-fish may be frozen with the water in its 

 vase, and yet by a slow application of heat, become as 

 lively as ever, in the course of half an hour. In these 

 cases, and many others which will be mentioned hereafter, 

 life is suspended, but its principle remains, and although 

 such animals do not preserve their temperature like those 

 of the higher orders, they are still endowed with a much 

 greater tenacity of life, for with a few exceptions, when a 

 warm-blooded animal becomes cold, the vital principle 

 is not merely suspended, but is extinct, and death en- 

 sues. 



205. The power of man, and also of quadrupeds and 

 birds, to resist changes of temperature, is indeed surprising. 

 With respect to the power of animals to resist low degrees 

 of temperature, every one who resides in a cold climate, 

 has seen abundance of natural examples. The turkey, for 

 instance, will sleep comfortably, perched on a high tree, 

 entirely exposed to the northern blast, when the thermom- 

 eter is thirty degrees below zero. Allowing the tempera- 

 ture of the bird to be one hundred degrees, which is not 

 above the truth, then there is a difference of one hundred 



What is said about the freezing of eels and fish? What animals have 

 the greatest tenacity of life, cold or warm-blooded? What difference 

 sometimes exists between the temperature of the turkey and the air in 

 which he is? 



7 



